Luxor Video Entertainment Computer (II?) - Fairchild channel f (II?)

[Hannes.e]

Troubleshooting a Luxor Video Entertainment Computer.

It has detachable controllers so it's a Luxor Video Entertainment Computer "II" I guess (?)

 

Is there some schematics for the Fairchild channel f II ?

The ones I have seen seems to relate to the first version.

 

When starting it I get video like on the attached photos, for a couple of seconds, then the video just cuts out and nothing more happens.

When I start it the first time after some rest, I get a couple of seconds more than after just a quick off/on (so I'm thinking some capacitors, possibly power supply is involved).

 

With somewhat limited electronics skills I have examined the 8-wire cable from the transformer/buttons board to the mainboard and my theory is that the pins are:

1. Power (unregulated 5V?) - 9.5V on my unit

2. Power (unregulated 12V?) - 19V on my unit 

3. MODE button

4. TIME button

5. HOLD button

6. RESET button

7. START button

8. GND

 

Any comments or tips on how to proceed is welcome ! 

 

 

 

[CatPix]

There have been "Gen I" PAL units but it seems that there is little relationship between the US models and the PAL ones. Most of them are probably Gen 2 but the only way to say for sure seems to check the CPU speed : it should be of 2 Mhtz on Versions 1 and 1.77 on versions 2 (but it's not written on them so...)

 

The first screen isn't highly significant as the Channel F tend to display garbage on screen until you refresh by pressing Reset. But it should stay on (BTW if you aren't aware, the console contain 2 built-in games so the screen will display a "G?" after resetting :

You press 1 or 2 to select it. I advise you to choose 1 because it's the famous Pong games that will allow  to test all the contacts on your joysticks. Plus it's very fun to play with a friend

 

Saba Videoplay models are notorious for suffering from defective power supplies.

 

For the power supplies, odd voltages weren't unknow back then (a quick example, the Bally Astrocade use a dual power supply which is 7.5V AC and 11.5V AC).

 

Oh well, I was going to look for scematics of the Videoplay, but there are schematics of the Luxor!

http://channelf.se/veswiki/index.php?title=Schematics

If this is the right one, and that the "power supply" part is about the board, then part of the power supply part is on the motherboard

 

It says "heatsink" for one of the regulators. Since I see no regulator on the power board, it mean that the voltage you get out of the cable are normal, and I would look where you have two "transistors" bolted on the metallic shield, on the top right part of your picture. Those looks like voltage regulators to me! You should check here and see if you get 19V in one and 12V out. Then on the other you should have 9V in and 5V out. And check if the voltage is stable. Those are regulators so the output should be very stable. Check if they don't overheat, I would be very suspicious of both, those regulators are a common cause of failure.

Those are most likely cheap and generic parts (the 7805 sure is, it's the same than in an Atari 2600 and the NES for example) so you can probably get spares ones easily and replace them just in case.

 

This schematics isn't for the Luxor but the power part seems to be identical, but much easier to read.

Edited March 6, 2021 by CatPix

[Hannes.e]

Thanks @CatPix 

 

Yes, those are voltage regulators bolted to the shielding.

They are actually socketed, so extremely easy to replace.

voltage level was a bit under 12V, around 11.85 on my multimeter, but that seems to be within the margins (a datasheet on a random 7812 said 11.5 - 12.5v was within spec).

 

Since I had a 7805 at home I thought I would replace it just in case, but when I was working with that the 5v disappeared completely, then it went back and forth a bit when I was handling the power board, like something was loose, so I didn't really trust it.

So instead I tried to replace the power supply with a combined 5v+12v supply in my box of old power supplies (think it came with some Logitech speakers).

(I connected the power supply to the cable from the power board, and replaced the regulators with wires)

 

With the "new" power supply the console work somewhat better: https://photos.app.goo.gl/2Nbyd9TcxaA24aqi8

I get the G? and when I cold start it I have time to select the game and see it start, but after something like 30s it cuts out completely like before.

I the video I connect the power, then the video cuts out, after that I disconnect and reconnect the power and it starts again, but this time it cuts out after only a few seconds.

(If I wait a while I can repeat this)

 

With the new power supply my multimeter indicates voltage levels are holding steady very close to 5 and 12 volts, but I guess It still could be disturbance on it the multimeter won't pickup. 

Anyone knows how much 5v and 12v would reasonably be consumed by a fairchild II ? My power supply is rated at 2A 5V + 2A 12V.

 

Do you think it could use the unregulated 5 and 12 volts for something, and be dependent on it being >5 and >12 ?

I'm thinking that since the Fairchild (I) has an external power supply with voltage regulators in the power supply unit (as I understand it) the mainboard shouldn't use the unregulated power...

 

Next steps are trying a bigger power supply (to rule out that the supply I found was to weak), I think I have a PC power supply somewhere, should be way more than enough.

I will also get a new 7812 voltage regulator and try the original supply again with new regulators.

 

But I am a bit concerned that there is something more/else that is wrong, since I still have the "cold start/warm start" effect.

 

Now when I'm writing this I realize there is also a small cable from the power board directly to the antenna output,

something about DC level on the antenna output perhaps, and I didn't replace that when I used the new power supply.

However, I still don't think that would cause the console to cut out after a while like it does.

 

 

[Tissemon]

On 3/6/2021 at 9:42 PM, Hannes.e said:

Thanks @CatPix 

 

Yes, those are voltage regulators bolted to the shielding.

They are actually socketed, so extremely easy to replace.

voltage level was a bit under 12V, around 11.85 on my multimeter, but that seems to be within the margins (a datasheet on a random 7812 said 11.5 - 12.5v was within spec).

 

Since I had a 7805 at home I thought I would replace it just in case, but when I was working with that the 5v disappeared completely, then it went back and forth a bit when I was handling the power board, like something was loose, so I didn't really trust it.

So instead I tried to replace the power supply with a combined 5v+12v supply in my box of old power supplies (think it came with some Logitech speakers).

(I connected the power supply to the cable from the power board, and replaced the regulators with wires)

 

With the "new" power supply the console work somewhat better: https://photos.app.goo.gl/2Nbyd9TcxaA24aqi8

I get the G? and when I cold start it I have time to select the game and see it start, but after something like 30s it cuts out completely like before.

I the video I connect the power, then the video cuts out, after that I disconnect and reconnect the power and it starts again, but this time it cuts out after only a few seconds.

(If I wait a while I can repeat this)

 

With the new power supply my multimeter indicates voltage levels are holding steady very close to 5 and 12 volts, but I guess It still could be disturbance on it the multimeter won't pickup. 

Anyone knows how much 5v and 12v would reasonably be consumed by a fairchild II ? My power supply is rated at 2A 5V + 2A 12V.

 

Do you think it could use the unregulated 5 and 12 volts for something, and be dependent on it being >5 and >12 ?

I'm thinking that since the Fairchild (I) has an external power supply with voltage regulators in the power supply unit (as I understand it) the mainboard shouldn't use the unregulated power...

 

Next steps are trying a bigger power supply (to rule out that the supply I found was to weak), I think I have a PC power supply somewhere, should be way more than enough.

I will also get a new 7812 voltage regulator and try the original supply again with new regulators.

 

But I am a bit concerned that there is something more/else that is wrong, since I still have the "cold start/warm start" effect.

 

Now when I'm writing this I realize there is also a small cable from the power board directly to the antenna output,

something about DC level on the antenna output perhaps, and I didn't replace that when I used the new power supply.

However, I still don't think that would cause the console to cut out after a while like it does.

I'm reviving an old thread here, but did you ever get it to work? And if so, what was wrong with your console?